1. FIELD OF THE INVENTION
This invention relates to an improved process for preparing ethanol from methanol by reaction with hydrogen and carbon monoxide.
2. PRIOR ART
A great number of processes have been described in the art for reacting methanol with carbon monoxide and hydrogen in the presence of catalyst systems to produce ethanol. A general disadvantage of the art described processes is that they all produce a wide variety of other related products such as higher molecular weight alcohols, aldehydes, ketones, carboxylic acids, esters, etc. in addition to the desired ethanol.
In U.S. Pat. No. 3,285,948, for example, a method of forming alcohols is set out in which a cobalt catalyst system comprising cobalt carbonyl, an iodine promoter and a ruthenium halide is described. Cawse discloses in U.S. Pat. No. 4,013,700 a process for preparing polyhydric alcohols, etc. by reacting hydrogen and carbon monoxide in the presence of a quaternary phosphonium salt and a rhodium carbonyl at elevated temperature and pressure. Riley et al teach in U.S. Pat. No. 3,248,432 the preparation of ethanol by the reaction of methanol, carbon monoxide, and hydrogen in the presence of a cobalt compound and an iodine promoter. Likewise in British Pat. No. 1,546,428 the preparation of ethanol by reacting methanol with carbon monoxide and hydrogen in the presence of a solvent such as hydrocarbon solvent, a cobalt-containing catalyst such as cobalt iodide or bromide and a tertiary phosphine. Slinkard in U.S. Pat. No. 4,168,391 teaches a process for preparing ethanol by reaction of carbon monoxide, hydrogen and methanol in the presence of cobalt carbonyl and an oxygenated solvent such as dioxane.
All of the processes described above suffer from one or more disadvantages. In most cases the conversion of methanol is low and a wide variety of products in addition to the desired ethanol are formed with consequent separation and disposal problems.